This invention relates to artificial organ assemblies which are suitable for heat-sterilization with, for example, an autoclave and which eliminate the need for treatments after sterilization, and the sterilization method thereof.
Artificial organ assemblies include, for example, a blood dialysis apparatus which interposes a semipermeable membrane between the blood and a dialysate to extract waste materials and excessive water from the blood into the dialysate. This apparatus is generally called an artificial kidney. Today, blood dialysis apparatus are classified according to their structural characteristics into the coil type, plate type and hollow (tubular) fiber type. Among these, the hollow fiber type blood dialysis apparatus has been widely used due to its more efficient dialysis and the smaller amount of filling liquid required, as well as other advantageous characteristics.
However, the blood dialysis apparatus of the hollow fiber type has about 10,000 fibers of regenerated cellulose for example, bundled together and having an internal diameter between about 200 and 300.mu.. The blood flows inside each fiber and the dialysate flows outside the fibers, so that there are many problems in sterilization. In other words, in dry sterilization, such as gamma rays or gas sterilization with ethylene oxide, liquid passage is very irregular because the hollow fibers constitute extremely thin capillaries, keeping bubbles therein, and much labor is needed to eliminate bubbles inside the fibers. If the blood dialysis apparatus is first filled with a liquid and offered as a package, labor can be saved and the performance of the hollow fibers can be maintained constant. As an example of such an approach, a wet sterilization method is known wherein liquid sterilizer such as formalin is filled into the apparatus. In the case of formalin sterilization, however, there is a fear that a residue of the sterilizer may remain in the blood dialysis apparatus. To avoid this, a method has been proposed wherein such chemicals as mentioned above are not used, but a physiological saline solution is filled into the artificial organ as described above, and sterilization is carried out in an autoclave under pressure and heat. In this case, there is a fear that cracking or breakdown of the artificial organ may occur with heat expansion of the filled physiological saline solution or other causes, which poses a problem. As a solution to this problem, a method has been proposed wherein a buffer sack attached with a cannula is passed through either the blood port or the dialysate port of the artificial organ, and sterilization is carried out in this state; then the buffer sack is removed and the artificial organ is packed, followed by sterilization with ethylene oxide gas. Alternatively, a method has been proposed wherein a deformable baggy cap is provided as a stopper for either the blood port or the dialysate port of the artificial organ; after sterilization in an autoclave, the baggy cap is removed and replaced with a conventional rubber stopper, followed by packing in an aseptic environment. In these methods are, however, the process between the autoclave sterilization and the achievement of a sterilized package is cumbersome and requires much labor, and the fear of recontamination remains during the treatment following the autoclave sterilization. In other words, in the former method using a buffer sack with a cannula, contamination by mold or germs is possible at the site where the cannula pierces, and in the former method using a baggy stopper, the difficulties of replacing the baggy stopper with a normal cap and of packaging in a perfectly aseptic environment pose problems. Moreover, because these conventional methods involve cooling with water after the autoclave sterilization prior to packing, contamination at this stage must also be considered.
This invention was made in consideration of the situation stated above, and aims to offer artificial organ assemblies that are suitable for sterilization under pressure and heat by such means as an autoclave, to eliminate the need for treatment after sterilization and to require only simple preparation, and a method for sterilization of the assemblies.
Further, this invention aims to provide artificial organ assembly packages that permit rapid heat-sterilization, and further allow a required humidity to be maintained after sterilization.